C++重载运算符和重载函数是什么

#include <iostream>
using namespace std;
 
class printData
{
  public:
   void print(int i) {
    cout << "整数为: " << i << endl;
   }
 
   void print(double f) {
    cout << "浮点数为: " << f << endl;
   }
 
   void print(char c[]) {
    cout << "字符串为: " << c << endl;
   }
};
 
int main(void)
{
  printData pd;
 
  // 输出整数
  pd.print(5);
  // 输出浮点数
  pd.print(500.263);
  // 输出字符串
  char c[] = "Hello C++";
  pd.print(c);
 
  return 0;
}

#include <iostream>
using namespace std;
 
class Box
{
  public:
 
   double getVolume(void)
   {
     return length * breadth * height;
   }
   void setLength( double len )
   {
     length = len;
   }
 
   void setBreadth( double bre )
   {
     breadth = bre;
   }
 
   void setHeight( double hei )
   {
     height = hei;
   }
   // 重载 + 运算符，用于把两个 Box 对象相加
   Box operator+(const Box& b)
   {
     Box box;
     box.length = this->length + b.length;
     box.breadth = this->breadth + b.breadth;
     box.height = this->height + b.height;
     return box;
   }
  private:
   double length;   // 长度
   double breadth;   // 宽度
   double height;   // 高度
};
// 程序的主函数
int main( )
{
  Box Box1;        // 声明 Box1，类型为 Box
  Box Box2;        // 声明 Box2，类型为 Box
  Box Box3;        // 声明 Box3，类型为 Box
  double volume = 0.0;   // 把体积存储在该变量中
 
  // Box1 详述
  Box1.setLength(6.0); 
  Box1.setBreadth(7.0); 
  Box1.setHeight(5.0);
 
  // Box2 详述
  Box2.setLength(12.0); 
  Box2.setBreadth(13.0); 
  Box2.setHeight(10.0);
 
  // Box1 的体积
  volume = Box1.getVolume();
  cout << "Volume of Box1 : " << volume <<endl;
 
  // Box2 的体积
  volume = Box2.getVolume();
  cout << "Volume of Box2 : " << volume <<endl;
 
  // 把两个对象相加，得到 Box3
  Box3 = Box1 + Box2;
 
  // Box3 的体积
  volume = Box3.getVolume();
  cout << "Volume of Box3 : " << volume <<endl;
 
  return 0;
}